September 24, 2013
04:15 PM (EDT)

News Release Number: STScI-2013-40

September 24, 2013: Astronomers may have found the densest galaxy in the nearby universe.
The galaxy, known as M60-UCD1, is located near a massive elliptical
galaxy NGC 4649, also called M60, about 54 million light-years from
Earth. This composite image shows M60 and the region around it, where
data from NASA's Chandra X-ray Observatory are pink and data from
NASA's Hubble Space Telescope are red, green, and blue. The Chandra
image shows hot gas and double stars containing black holes and
neutron stars, and the Hubble image reveals stars in M60 and
neighboring galaxies including M60-UCD1. The arrow points to M60-UCD1.

Packed with an extraordinary number of stars, M60-UCD1 is an "ultra-compact
dwarf galaxy." It is one of the most massive galaxies of its kind, weighing
200 million times more than our Sun, based on observations with the Keck
10-meter telescope in Hawaii. Remarkably, about half of this mass is
found within a radius of only about 80 light-years. This would make the
density of stars about 15,000 times greater than found in Earth's
neighborhood in the Milky Way, meaning that the stars are about 25
times closer. For more information about M60-UCD1, visit
http://chandra.si.edu/press/13_releases/press_092413.html .